Support of Unions

[a-marcel]

Hello,

if i try to create a union Type

type Foo {
  name: String
}
union SingleUnion = Foo
type Root {
  single: SingleUnion
}

an error occurs

RootTypeProvider.java:[3,60] cannot find symbol
[ERROR] symbol:   class SingleUnion

Marcel

[a-marcel]

Hello,

i see in the code that you support Unions in general, but for my line above, the file is not written.

Do you've any idea ?

Thanks
Marcel

[brimworks]

We can parse schemas with Union types, we just need to add logic in here:

https://github.com/Distelli/graphql-apigen/blob/master/apigen/src/main/resources/graphql-apigen.stg

...so it can generate the union types. Something like this:

unionTypeFileName(model) ::= "<if(model.unionType)><model.name>.java<endif>"
unionTypeGenerator(model) ::= <<
package <model.packageName>;
...
>>

Feel free to take a stab at it.

Cheers,
-Brian

[brimworks]

...and of course you will also want to write a TypeProvider:

unionTypeProviderFileName(model) ::= "<if(model.unionType)><model.name>TypeProvider.java<endif>"
unionTypeProviderGenerator(model) ::= <<
...
>>

[a-marcel]

The type should be something like this

GraphQLUnionType PetType = newUnionType()
        .name("Pet")
        .possibleType(CatType)
        .possibleType(DogType)
        .typeResolver(new TypeResolver() {
            @Override
            public GraphQLObjectType getType(TypeResolutionEnvironment env) {
                if (env.getObject() instanceof Cat) {
                    return CatType;
                }
                if (env.getObject() instanceof Dog) {
                    return DogType;
                }
                return null;
            }
        })
        .build();
    

[a-marcel]

Hello,

i build some Object Local:

my schema:

interface DefaultPage {
	id: String
	url: String
}

type Contact implements DefaultPage {
	id: String
}

union Page = Contact

type helloWorldQuery {
	page(url: String): [Page]
}

i added in the generated Guice Binder:

  types.addBinding("Page")
                .toProvider(...PageTypeProvider.class);

create a PageTypeProvider

import javax.inject.Inject;
import javax.inject.Provider;

import com.distelli.graphql.MethodDataFetcher;

import graphql.Scalars;
import graphql.schema.GraphQLFieldDefinition;
import graphql.schema.GraphQLObjectType;
import graphql.schema.GraphQLUnionType;
import graphql.schema.TypeResolver;

public class PageTypeProvider implements Provider<GraphQLUnionType> {

	@Inject
    protected ContactTypeProvider contactProvider;

	
	@Override
	public GraphQLUnionType get() {
		
		return GraphQLUnionType.newUnionType()
				.name("Page")
				.possibleType(contactProvider.get())
				
				.typeResolver(new TypeResolver() {

					@Override
					public GraphQLObjectType getType(Object object) {
						return contactProvider.get();
					}
		          
		        })
				.build();
	}

}

possibleType is repeatable.
i guess here it's better to have a MultiBindingGuice typeResolver.

and i create a Page object

public interface Page {

	public static class Builder {

		private String _id;

		public Builder() {
		}

		public Builder(Page src) {

			_id = src.getId();

		}

		public Builder withId(String _id) {
			this._id = _id;
			return this;
		}

		public Page build() {
			return new Impl(this);
		}
	}

	public static class Impl implements Page {

		private String _id;

		protected Impl(Builder builder) {

			this._id = builder._id;

		}

		@Override
		public String getId() {
			return _id;
		}

		@Override
		public String toString() {
			return "Page{"

					+ "id=" + _id

					+ "}";
		}
		// TODO: equals(Object) & hashCode()
	}

	public default String getId() {
		return null;
	}
}

and i bind a custom HelloWorldQuery class.

I pick all information from https://medium.com/the-graphqlhub/graphql-tour-interfaces-and-unions-7dd5be35de0d

my Query is:

{"query":"{page(url: \"xxx\") { ... on Contact {id}}}

Your stg file is a little complex for me and i'm new in graphql. i hope, it help a little bit :/

Thanks for your work, it helps me a lot, to create a clean service without writing all this JavaClasses.

Marcel

[brimworks]

Thanks Marcel, how do you want the Page interface to interact with the various union types? I was thinking that it would generate various type specific methods which return null unless the union holds a value of that type.

So PageTypeResolver would need to look something more like this if there was two types in the union (aka union Page = Contact | OtherPage):

public class PageTypeProvider implements Provider<GraphQLUnionType> {

	@Inject
    protected ContactTypeProvider contactProvider;
	@Inject
    protected OtherPageTypeProvider otherPageProvider;

	
	@Override
	public GraphQLUnionType get() {
		
		return GraphQLUnionType.newUnionType()
				.name("Page")
				.possibleType(contactProvider.get())
				.possibleType(otherPageProvider.get())
				.typeResolver(new TypeResolver() {

					@Override
					public GraphQLObjectType getType(Object object) {
						Page page = (Page)object;
						if ( null != page.getContact() ) {
						    return contactProvider.get();
						if ( null != page.getOtherPage() ) {
						    return otherPageProvider.get();
						} // TODO: What is the default? what if we return null here?
					}
		          
		        })
				.build();
	}

}

...and the Page class generated would have get fields for getContact() and getOtherPage().

What are your thoughts?

[brimworks]

...or alternatively we generate an enum for the type of value held by the union, and have a special method to obtain that... so the getType() method becomes:

@Override
public GraphQLObjectType getType(Object object) {
    Page page = (Page)object;
    switch ( page.type() ) {
    case Contact: return contactProvider.get();
    case OtherPage: return otherPageProvider.get();
    }
    throw new IllegalStateException("Unknown type="+page.type());
}

...also, don't we need a way to obtain the value for the union type? ...with a data binder?

[a-marcel]

Hi, thanks for your answer.

one question, i can answer: it's possible to return null in getType (https://github.com/graphql-java/graphql-java - look at union type).

from my pov its not necessary to create a "type" property because the developer/creator of the schema should know if he need it or not. the getType function should just check if the Object object a valid type and return the mapped provider.

for the data question, i check this now and come back to you.

Marcel

[a-marcel]

Hello again,

it's not possible to return null for the getType. If you return null, graphql will fail because he cannot detect the type.

I found two links

https://github.com/graphql-java/graphql-java/blob/f493a19cdd99a78b14bda976aba2e00f47881894/src/test/groovy/graphql/UnionTest.groovy

https://github.com/graphql-java/graphql-java/blob/master/src/test/groovy/graphql/GarfieldSchema.java

in general my classes looks like this, but my response is always empty:

{"data":{"page":[{}]},"error":[]}

if i return multiple objects in my HelloWorldQuery it returns multiple empty objects

public class HelloWorldQuery implements helloWorldQuery {
	@Override
	public List<Object> page(PageArgs args) {
		
		String url = args.getUrl();

		List<Object> res = new ArrayList<Object>();

		res.add(new Contact.Builder().withId("123").build());
		res.add(new Contact.Builder().withId("123").build());

		return res;
	}
}

but i'm not able to get the expected:

query:

{page(url: \"xxx\") { ... on Contact { id }}}

i expect:

{"data":{"page":[{id: "123"}]},"error":[]}

maybe you've an idea, but in general i looks like it works, but graphql filter my objects.

Thanks
Marcel

[a-marcel]

Hello again,

i changed my old hello world example to an union graphql example

https://github.com/marcelalburg/vertx_graphql_hello_world_example (includes a test for simple startup)

i created manually : https://github.com/marcelalburg/vertx_graphql_hello_world_example/blob/master/src/main/generated/com/example/apigen/Page.java

https://github.com/marcelalburg/vertx_graphql_hello_world_example/blob/master/src/main/generated/com/example/apigen/PageTypeProvider.java

changed the getPage method to Object (because i like to return different objects) in:
https://github.com/marcelalburg/vertx_graphql_hello_world_example/blob/master/src/main/generated/com/example/apigen/helloWorldQuery.java

and changed the impl of the query:
https://github.com/marcelalburg/vertx_graphql_hello_world_example/blob/master/src/main/java/com/example/guice/HelloWorldImpl.java

this returns currently a Contact Type with some values.

In this example the query returns just [].

maybe you've an idea, because i think, that i don't understand your concept correctly (and i'm still not fit in understanding the java-graphql implementation).

Thanks for your help

Marcel

[a-marcel]

Hello again,

sorry for all this messages. But i found the issue now.

i've written a test:

https://github.com/marcelalburg/vertx_graphql_hello_world_example/blob/master/src/test/java/com/example/RawGraphQLWithApiGenObjectsTest.java

There are some issues. The biggest is, that the Guice Provider is always returning a new Instance of a Graphql Type and this is not working together with unions. So, i make my ContactTypeProvider to a Singleton and it works perfectly.

The second one is, it's a nice to have to support interfaces.

I wrote everything for interfaces and the Union Provider and hope you can use it to implement it in your generation file.

This singleton is maybe not the best idea and i hope you've some other nice idea to return always the same instance of a type.

I ask in the GraphQL github, why there is an issue with references in Union Types. I hope they have an idea, so that you don't need to inject provider for the possible types in a union.

Thanks
Marcel